Tuesday, February 07, 2017

New Study Concludes that Vaping is a One-Way Bridge to Cigarette Smoking among Youth

A new study
published online ahead of print in the journal Tobacco Control concludes that vaping is “a one-way bridge to
cigarette smoking among youth.”

(See: Miech R, Patrick ME, O’Malley
PM, Johnston LD. E-cigarette
use as a predictor of cigarette smoking: results from a 1-year follow-up of a national sample of 12th grade students. Tobacco Control.http://dx.doi.org/10.1136/tobaccocontrol-2016-0532910).

The study involved a one-year follow-up of 347 high school
seniors who were surveyed at baseline in 2014 and at follow-up in 2015. At baseline,
they were classified as recent vapers (used an e-cigarette in the past 30 days)
or non-vapers. At follow-up, smoking initiation was defined as having smoked a
cigarette in the past year.

In the key analysis, smoking initiation (smoking a cigarette
in the past year) was compared between recent vapers (used an e-cigarette in
the past 30 days) and non-vapers who had never smoked at the time of the
baseline survey. The paper reports that the rate of smoking initiation was 31%
among the recent vapers and 7% among non-vapers. In an adjusted analysis,
recent vapers were 4.8 times more likely than non-vapers to initiate smoking
during the follow-up period.

The paper concludes that “vaping is a one-way bridge to
cigarette smoking among youth.”

The Rest of the Story

At first glance, this paper appears to demolish the claim
that vaping is not a known gateway to youth smoking. The conclusion that is
drawn is a sweeping one: e-cigarettes are a one-way bridge to cigarette smoking
among youth. If this conclusion is true, then I believe e-cigarettes are not a
tenable harm reduction strategy because the benefits of adults quitting using
e-cigarettes would be offset by a substantial increase in youth becoming
addicted to smoking and possibly suffering life-long health effects, disease,
disability, and premature death.

So am I going to renounce my earlier conclusions (that there
is no evidence vaping causes kids to start smoking)?

Perhaps, but not without a closer look at the study.

To be a valid conclusion, there must not be a plausible, alternative
explanation for the study findings. The paper does not present any alternative
explanations. But this doesn’t mean that there isn’t one.

In fact, there is a very plausible (and in fact, highly
likely) alternative interpretation of these findings:

Experimenting with e-cigarettes is a sensitive marker of substance-related,
risk-taking behavior in general, which strongly predisposes a youth to trying
cigarettes.

What could easily explain the observed findings is that
youth who experiment with e-cigarettes are also more likely to experiment with
other substances, including cigarettes. Therefore, of course you are going to
find a higher rate of cigarette experimentation among youth who have already
experimented with electronic cigarettes. This should come as a surprise to no
one.

The observed relationship between e-cigarette
experimentation and cigarette experimentation could well be a spurious one,
confounded by an underlying predisposition to substance-related, risk-taking
behavior. Importantly, the study did not make any attempt to control for any
measures of risk-taking behavior. Moreover, the study did not even control for
underlying susceptibility to smoking.

There are two additional and related factors that cast
serious doubt on the study’s conclusion.

First, the exposure variable – recent vaping – was defined
as having tried even one e-cigarette in the past month. All we know about the
baseline “vapers” is that they had taken a puff on an e-cigarette in the past
month. We do not know that they were regular vapers. We do not know that they
had become addicted to nicotine or to vaping. We don’t even know that they had
tried vaping more than once in their entire life! So to conclude that this
study demonstrates that vaping is a one-way bridge to smoking is not warranted.

Second, the outcome variable – smoking initiation – was defined
as having tried even one cigarette in the past year. All we know about the
smoking initiators is that they had taken a puff on a cigarette in the past
year. We don’t even know that they had tried more than one cigarette in the
past year. So to conclude that vaping is a bridge to smoking based on this
definition is not warranted.

The question that arises is why the study did not examine
whether frequent vapers were more
likely to progress to regular smoking (or at very least, current or established
smoking). According to the paper, the sample size was not large enough to allow
such an analysis. But that raises the question: If the sample size was not
large enough to allow an analysis of frequent vapers, was it large enough to
allow an analysis of all vapers? And most critically, how many youths were
there who were nonsmoking, recent vapers at baseline who tried a cigarette in
the next year? After all, this is the sample upon which the entire conclusion
of the study is based.

So I took a closer look at the study – well, not the actual
study because the sample size of baseline nonsmokers who had recently vaped is
not reported anywhere in the study. You have to go to a separate, online appendix
to find this out.

So take a guess: How many youths is the sweeping conclusion
of this paper based on? (i.e., how many nonsmoking, recent vapers at baseline
progressed to having tried a cigarette at follow-up?)

a. 122
b. 84
c. 42
d. 21
e. 9

If you guessed E (9) ...

… then you are wrong.

The correct answer is none of the above. The total number of
nonsmoking, recent vapers who tried a cigarette in this study appears to be
just 4!

So you mean to tell me that the sweeping conclusion of this
paper – that vaping is a one-way bridge to smoking – is based on 4 youth?
Moreover, on 4 youth about whom all we know is that they tried an e-cigarette
during the month prior to the baseline survey and then tried a cigarette in the
following year. That hardly seems like a sufficient sample of youth upon which
to rely to formulate national policy.

In fact, there were apparently only 13 nonsmokers who were
recent vapers in the entire study of 347 youth. That itself should tell you
something. Namely, that it is very difficult to find nonsmokers who vape with
any significant frequency. In other words, e-cigarette experimentation is not any
kind of significant bridge to youth smoking because it doesn’t even appear to
be a bridge to regular or frequent vaping.

The rest of the story is that far from providing evidence
that vaping is a one-way bridge to cigarette smoking among youth, this study
provides further evidence that e-cigarette experimentation among nonsmoking
youth doesn’t even appear to be a bridge to regular vaping. It is very
difficult to find nonsmoking youth who experiment with e-cigarettes and then
progress to become frequent vapers. In fact, it’s such a rare phenomenon that
this study failed to achieve a high enough sample size to even analyze the rate
at which these nonsmoking frequent vapers progressed to smoking. That itself is
really the key finding of the paper.

This story illustrates why you have to be very careful in reading
and interpreting the scientific literature. If you didn’t look at the supplemental
material, which was not part of the article itself, you would never even be
aware that the sweeping conclusions of this study were based on 4 kids.

All I can say is that when the FDA commissioner
signs his first order putting a vape shop out of business, these 4 kids should
be invited to the signing ceremony. Because it’s based on those 4 kids that
vaping opponents apparently would like us to formulate national smoking policy.

1 comment:

About Me

Dr. Siegel is a Professor in the Department of Community Health Sciences, Boston University School of Public Health. He has 32 years of experience in the field of tobacco control. He previously spent two years working at the Office on Smoking and Health at CDC, where he conducted research on secondhand smoke and cigarette advertising. He has published nearly 70 papers related to tobacco. He testified in the landmark Engle lawsuit against the tobacco companies, which resulted in an unprecedented $145 billion verdict against the industry. He teaches social and behavioral sciences, mass communication and public health, and public health advocacy in the Masters of Public Health program.